1. Field of the Invention
The present invention relates to an automatic belt tightener and, more particularly, to a belt drive mechanism for transmitting torque between a driver and a rotatable member to be driven thereby, making use of such an automatic belt tightener and drive mechanism for ensuring transfer of torque between the driver and the driven member and, further, for automatically taking up any slack that may be present in such a belt drive arrangement.
2. Description of the Prior Art
The rotational velocity of an element being rotated, such as the drum of a domestic clothes dryer, is oftentimes critical and is necessary to be kept within given small tolerances in order to maintain the proper tumbling of clothes in the drum. This is especially so since the outside diameter or surface of the dryer tumbling drum is commonly used as a large pulley. Various belt tightener mechanisms have been utilized in the past for rotating the clothes dryer drum. An example is found in U.S. Pat. No. 3,330,049. Typically, such an arrangement involves the belt being driven by a single pulley attached to the motor shaft. An idler pulley assembly is utilized to provide belt tension; however, it has no driving capabilities. Another automatic belt tightener mechanism is shown in U.S. Pat. No. 3,864,986, assigned to the same assignee as the present application, wherein a mechanism is shown which has a roller assembly which pivots about the rotational axis of the driving member in a direction corresponding to the direction of rotation of the driving member for allowing any slack in the belt to be taken up automatically. Again, the belt is being driven by a single driving member, namely the motor shaft. It is desirable in a belt drive mechanism to have the belt driven not only by the driving member but by other members to thereby increase the frictional surface contact with the belt, thus imparting maximum torque transfer to the belt with a minimum of slipping.
Furthermore, in production application, a tolerance is necessary in belt lengths; and means, preferably automatic, must be provided for taking up the slack that may result in a belt drive system due to this tolerance. Also, with use and age, the belt tends to lengthen and it is desirable that means should be provided for automatically taking up the slack that results.
The prior art has taught the use of idler roller tensioners, as mentioned above, which are usaully spring-loaded to effect this operation. One such application is also shown in U.S. Pat. No. 3,211,015 -Bochan, assigned to the same assignee as the present invention. There is, however, no suitable, low-cost way of combining the functions of taking up the belt slack and increasing the frictional drive engagement automatically, thereby eliminating the idler roller tensioners.
By the present invention, these deficiencies may now be overcome and the mechanism of the invention is highly reliable, efficient, and of low cost.